Method for the removal of aflatoxin from cereals, oil seeds and feedstuffs

ABSTRACT

A method for the removal of Aflatoxin from materials including cereals, oil seeds and feedstuffs contaminated therewith comprising contacting said materials with a mixed solvent system of liquid dimethyl ether and water. The water is employed in an amount of 2 to 8 % by weight with respect to the liquid dimethyl ether. Such method which can reduce the Aflatoxin content to 15 ppb or less, can be conducted at low temperatures so that no proteins contained therein are denaturated. Further, the spent solvent system containing Aflatoxin can be easily regenerated by contacting it with activated carbon and recycled.

This invention relates to a method for the removal of Aflatoxin fromcereals, oil seeds and feedstuffs which are contaminated therewith, bythe use of a mixed solvent system comprising liquid dimethyl ether andwater. More particularly, this invention relates to a method for thecomplete removal or elimination of a carcinogenic poisonous substanceproduced by a mold, which is named "Aflatoxin", from those cereals, oilseeds and feedstuffs contaminated with said substance through extractionin an extraction system containing liquid dimethyl ether and water.

The term "cereal" as used herein means to refer to any cereals, whichare normally ingestable orally in any optional form of raw or processedgrains and meals such as rice and so on. The term "oil seed" as usedherein means to refer to any oil seeds, which are normally edible in anyoptional form of raw or processed grains, meals and cakes, such aspeanut, peanut meal, cotton seed, cotton seed meal, cotton seed cakesand so on. The term "feedstuff" as used herein refers to any othermaterials which may be employed for preparing a feed of domesticanimals.

It is well-known in the art of Aflatoxin is one sort of those toxinsproduced by a variety of molds, of an extremely high carcinogenicity anda typical one produced by a microbe belonging to Aspergillus flavus andgrowing on foodstuffs such as grains. It is generally realized that suchmaterials as peanuts, cotton seeds, rice and the like are easilysusceptible to contamination with this toxin and thus badly damagedthereby.

Such foodstuffs or feedstuffs are generally classified into those for afood, a feed and others not employed for a feed, in accordance with theprescribed regulations which may vary depending upon the respectivecountries. Generally speaking, those stuffs containing Aflatoxin at aconcentration not less than 30 ppb are considered as improper for a foodas announced from WHO and FAO. According to the latest report from FDA,a lower content, namely not more than 15 ppb, on Aflatoxin has beensettled for a food in U.S.A. in view of the fact that the Aflatoxinpossesses a remarkably high carcinogenic activity.

It is, however, said that an extremely high level of contamination withAflatoxin in products tends to be made in a peanut- or cottonseed-producing district in the world, especially in the area where anatmospheric temperature is rather higher and also that approximately 25%of harvested peanuts contain Aflatoxin at a concentration beyond theregulated limit even in U.S.A. Even if the product contaminated withAflatoxin is not applied for a food but a feed, domestic fowls orpoultries are particularly sensitive to Aflatoxin and thus liable tohave carcinogenesis even at a lower concentration thereof.

Furthermore, from the contaminated peanuts or cotton seeds are generallyextracted the corresponding oils by means of, what is called, a prepresssolvent method, but Aflatoxin is unable to be extracted with an oilextracting solvent commonly employed for such purposes, which results inan increased concentration of Aflatoxin to approximately twice or morein the so produced oil cake or meal. These highly contaminated cakes ormeals should be, therefore, utilized solely for a fertilizer or burnt upwithout any possibility of being used for a feed. For instance, it isreported in "AFLATOXIN Food Science and Technology" by Leo A. Goldbatt(Acedemic Press), page 351 that extraction of raw peanuts containing5,500 ppb of Aflatoxin with n-hexane leaves peanut meal of an increasedAflatoxin concentration of 11,000 ppb and also extraction of said rawpeanuts by the press method only leaves peanut meal of an Aflatoxinconcentration of 7,000 ppb. These meals are obviously to be regarded asunsatisfactory for a feedstuff.

There have heretofore been proposed various methods for the removal ofAflatoxin from peanuts or cotton seeds contaminated therewith.Representatives of these prior methods may be summarized as hereunder.

1. A method for the chemical or physical decomposition of Aflatoxin; and

2. A method for the removal of Aflatoxin through extraction with asolvent.

In the above-mentioned method (1), the decomposition is generallyaccomplished by the use of an alkali. However, this method has not yetbeen commercially utilized, since it is difficult to demonstrate anontoxicity of a decomposition product and, more significantly, proteinsin the meal are proved to be decomposed and denaturated.

With respect to the above-mentioned method (2), there have beensuggested a wide variety of procedures, but they are also notcommercially utilized owing to respective drawbacks inherent therein.Common and most serious drawback is said to reside in its increasingcost, since a mixed solvent system comprising several sorts of differentsolvents should be used for the removal of Aflatoxin, different solventsystems should be applied to an oil-extraction step and anAflatoxin-extraction step, respectively, and denaturation of proteinsinvolved in a meal tends to proceed due to the use of an extremely highpolar solvent and application of a considerably elevated temperature tothe extraction step with said solvent and the removal step of saidsolvent.

As a result of our extensive studies in order to overcome or mitigatethe above-mentioned drawbacks and difficulties in the prior art, it hasbeen unexpectedly found that a carcinogenic substance, Aflatoxin, can beeffectively removed or eliminated from cereals, oil seeds and feedstuffscontaminated therewith by the use of a mixed solvent system of liquiddimethyl ether and water and this invention has been completed upon thisfinding.

It is, accordingly, a primary object of this invention to provide aneffective and advantageous technique for the removal of Aflatoxin fromcereals, oil seeds and feedstuffs contaminated therewith.

Other objects and advantages of this invention will become apparent fromthe following disclosure.

According to this invention, there is provided a new and improved methodfor the removal of Aflatoxin from cereals, oil seeds and feedstuffscontaminated therewith which comprises subjecting said cereals, oilseeds and feedstuffs to extraction in an extraction system containingliquid dimethyl ether and water at temperatures not higher than those atwhich any proteins in said materials are thermally denaturated, saidwater being employed in an amount of 2 to 8% by weight with respect tothe liquid dimethyl ether.

The raw materials to which the present method may be applied are, asmentioned above, cereals, oil seeds and other feedstuffs which arecontaminated with Aflatoxin. Typical examples thereof are raw peanuts,peanut meals, raw cotton seeds, cotton seed meals, cotton seed cakes andrice grains. It is to be noted that the raw materials may be of a rawstate and, alternatively, of a defatted meal form available from anoil-extraction factory.

The liquid dimethyl ether to be employed in the extraction system of thepresent method, is a solvent having a boiling point of -24.9° C., a weakpolarity and a strong oil-extractability capable of dissolving 6.1% byweight of water at 20° C.

In the extraction system, the water content may be 2 - 8% by weight,preferably 3 - 7% by weight with respect to liquid dimethyl ether. Inthis case, a preferable and sufficient extraction can be achieved byemploying 1 - 3 beds and 6 passes with respect to a raw material.

Extraction temperatures may be usually within the range of temperaturesnot higher than those at which any proteins in raw materials arethermally denaturated, as pointed out hereinabove, with temperaturesbelow ordinary temperature being preferred. Temperatures between 30° and-30° C. are practically preferable, but any higher or lower temperaturesmay be satisfactorily applied, if they are industrially desirable.

Removal or elimination of the extracting solvent from an extractionresidue may be easily conducted at temperatures below ordinarytemperature due to the boiling point of liquid dimethyl ether of -24.9°C., without any substantial denaturation of proteins during theprocessing.

In practicing the method of the present invention, a contaminated rawmaterial is pulverized or finely divided to a particle size of around 12mesh and placed into a pressure resistant vessel such as an autoclave.Subsequently, extraction is effected. When the Aflatoxin content of thematerial is as small as 50 ppb or less, that is, when the degree ofcontamination with Aflatoxin is very small, the removal of Aflatoxin maybe accomplished by extraction with liquid dimethyl ether alone due tooil and/or water contained in the material. In general, however, theeffective removal of Aflatoxin from the material is satisfactorily andefficiently attained by extraction in an extraction system containingliquid dimethyl ether and water. In order to realize the extraction inan extraction system containing liquid dimethyl ether and water, theremay be employed any method for adding two components, namely liquiddimethyl ether and water as long as both of liquid dimethyl ether andwater are present when extraction is effected. Illustratively stated,for example, there may be employed a method in which a required amountof water is added to liquid dimethyl ether to obtain a mixed solvent andthen the extraction is effected using such mixed solvent; or a method inwhich a required amount of water is first added to the material and thenliquid dimethyl ether is added in each extraction step. An amount ofwater to be added may vary depending upon the amount of liquid dimethylether employed, but it is desirable to use a saturating amount, namelyan amount corresponding to 6.1 g. (at 20° C.) with respect to 100 g. ofliquid dimethyl ether in each extraction step. For instance, where 1 kg.of a raw material of a water content 0% is employed, 2 kg. of liquiddimethyl ether per extraction and an amount of water corresponding to6.1% with respect to 2 kg. of said ether, namely 122 g. of water may beadded or, alternatively, an amount of water corresponding to 6.1% withrespect to the required amount of liquid dimethyl ether for six timesextractions, namely 732 g., of water is added before extractionprocedures and then extraction with liquid dimethyl ether alone may berepeated six times. In such procedures, each extraction is actuallyeffected with water-saturated liquid dimethyl ether owing to solubilityof only 6.1% water in liquid dimethyl ether and the remaining water isadsorbed in the raw material, which results in little effusion ofwater-soluble proteins. When six extractions are completed, said rawmaterial is dried approximately to its original state and Aflatoxin issimultaneously removed.

The amount of liquid dimethyl ether to be employed in the method of thepresent invention may vary depending upon the contamination level of theraw material as well as the degree of pulverization. Illustrativelystated, for example, when the material is pulverized to have a sizeabout 12 mesh and the method is carried out in a batchwise manner, the4-time, 5-time and 6 to 8-time repeated extractions using 2 to 3 beds ofliquid dimethyl ether are sufficient for complete removal of Aflatoxinfor the prewetted materials having Aflatoxin contamination levels of100, 300 and 500 ppb, respectively. When the material having the samepulverized size as above and the method is carried out in a continuousmanner, the relatively slow (at a linear velocity of about 4 mm/min.)contacts of the materials with 7, 9 and 12 beds of a mixed solventsystem of liquid dimethyl ether and water are sufficient for completeremoval of Aflatoxin from the materials having Aflatoxin contaminationlevels of 100, 300 and 500 ppb, respectively.

The extraction may be conducted using a method as ordinarily employed inthe extraction process, for example batchwise method, counter-flowmethod or the like.

All extracts from each step are passed through a suitable filter and theliquid dimethyl ether thus separated is evaporated with a slightheating, cooled, recovered and recycled to said vessel for reuse insubsequent extraction step. Such extraction procedures are repeated anumber of times. After completion of the extractions, the treated rawmaterial and the liquid dimethyl ether contained in the extracts arerecovered in a conventional manner as described above to afford anAflatoxin-free raw material, an oily phase containing Aflatoxin and anaqueous phase. Said oily and aqueous phases are easily separated bydecantation and the so separated oily phase is treated, for example, bya conventional alkali decomposition method to make Aflatoxin nontoxicand further subjected to oil refining treatment, thereby yieldingessential oil containing not more than 1 ppb of Aflatoxin.

According to the present method, simultaneous defatting and removal ofAflatoxin may also be effected with a raw material such as peanuts ofeither a raw or roasted state while keeping it in shape to afford thetreated material with an Aflatoxin content below the regulated limit.

For treatment of the aqueous phase containing Aflatoxin which isdischarged from the extraction system, we have also discovered that theAflatoxin dissolved in liquid dimethyl ether-water can be readilyremoved therefrom by the use of activated carbon due to its adsorptionactivity. This leads to resolution of a waste water problem as well asregeneration of an extracting solvent without any application ofdistillation. More specifically, after the material to be treated issubjected to extraction using a liquid dimethyl ether-water system toremove Aflatoxin therefrom, the liquid dimethyl ether-water systemcontaining Aflatoxin thus obtained can be treated as such with activatedcarbon for regeneration.

In practicing the adsorption of the Aflatoxin dissolved in the liquiddimethyl ether-water system, the amount of activated carbon to beemployed can be determined by taking into consideration an equilibriumadsorption amount of the activated carbon. When the concentration ofAflatoxin in the liquid dimethyl ether-water system is 72 ppm, theequilibrium adsorption amount is 42.5 μg./g. for powdered activatedcarbon and 48 μg./10 g. for spherical activated carbon. For example, foradsorbing 100 μg. of Aflatoxin extracted from 100 g. of peanuts havingan Aflatoxin concentration of 1 ppm with activated carbon, it issufficient to employ 2.5 to 3.5 g. of powdered activated carbon or 15 to25 g. of spherical activated carbon. The contacting time is preferably 5to 30 minutes. In this connection, it is noted that when the activatedcarbon type absorbing column is employed by connecting it to Aflatoxinextracting system, the liquid dimethyl ether-water system containingAflatoxin flows slowly and hence the Aflatoxin can be sufficientlycontacted with the activated carbon to be effectively adsorbed into thecarbon.

The mechanism of the removal of Aflatoxin according to the presentmethod is not fully understood, but it is believed to be as follows:

Generally, it has been heretofore believed that Aflatoxin is insolublein ethers. However, it was found to be soluble and extractable with themixed solvent system of liquid dimethyl ether and water, as set forthhereinabove. Removal of Aflatoxin at so much lower concentration thereofas expressed in terms of ppm -- ppb, which can be attained in thisinvention, is considered as distinctly different from dissolvability andextractability of the liquid dimethyl ether -- water system, to be dueto its activity of extruding or ejecting Aflatoxin from tissues of a rawmaterial such as peanuts or cotton seeds. Since liquid dimethyl etherhas a molecular weight of 46 and a diameter of not more than 5 A ittends to easily penetrate into tissues, as compared with other solvents.

According to our experiments, when raw peanuts and peanut meals(defatted cake obtained by a prepress method using n-hexane and dried tohave a water content of 0%), both of which had been contaminated with1,200 ppb of Aflatoxin, were each sufficiently contacted with liquiddimethyl ether alone at room temperature, it was found that theAflatoxin contamination level of the raw peanuts was reduced to about1,000 ppb while the Aflatoxin contamination level of the peanut mealscould not be reduced and retained at 1,200 ppb. Such difference wasfound to be affected by the extractable oil and, especially, watercontained in raw peanuts, leading to the method of this invention inwhich the contact of the Aflatoxin contaminated material with a liquiddimethyl ether -- water system brings about large reduction of theAflatoxin content to less than 15 ppb, namely the regulated limit inU.S.A. It is understood for us that the mechanism seems to be due toeither a promoted penetration into tissues with a small amount of waterincorporated in liquid dimethyl ether or dissociation and extrusion ofAflatoxin from tissues with liquid dimethyl ether and transportation ofthe dissociated Aflatoxin with a liquid dimethyl ether-water system.

Advantages of the present method may be summarized as indicated below.

1. One portion of Aflatoxin can be transferred into an aqueous phase andanother portion into an oily phase in the same vessel as used foroil-extraction with a mixture of the same extracting solvent, namelyliquid dimethyl ether and a small amount of water. In addition to theabove, the Aflatoxin transferred into an oily phase can be readilydecomposed to nontoxic state in a conventional manner to provideessential oil.

2. Extraction and removal of an extracting solvent system is feasible atlower temperatures.

3. Proteins are not substantially lost or denaturated.

4. Process can be industrially conducted at small cost, as compared withthe prior art using a mixed solvent system.

5. Far more effective extraction of oils can be accomplished.

This invention will be more fully illustrated by the following Examples,but they are not constructed to be limiting the scope of this invention.

EXPERIMENT 1

Raw peanuts (7.2% water content, 51.0% crude fat and 26.3% crudeprotein) contaminated with 450 ppb of Aflatoxin (B₁ and B₂) werepulverized by means of a mixer and then passed through a 12 mesh screento gather 150 g. of a peanut powder. The powder thus obtained wascharged into a 1 liter volume pressure resistant vessel equipped with amagnetic stirrer and extraction was carried out with 450 g. of liquiddimethyl ether at room temperature for 30 minutes with stirring. Aftercompletion of the extraction, the powder was separated from the liquiddimethyl ether solution containing Aflatoxin and again extracted with450 g. of fresh dimethyl ether in the same manner as shown above. Suchextraction was further repeated six times. After completion of the sixextractions, the powder was separated from the liquid dimethyl ether byfiltration and allowed to stand at 40° C and 10 mmHg for 1 hour toaccomplish a complete removal of residual dimethyl ether therefrom. Theresults are shown in Table 1. The Aflatoxin was determined according toa method prescribed by the Association of Official Analytical Chemists(frequently referred to herein as AOAC method) which comprisesextraction with methanol -- 1% aqueous sodium chloride (55:45 byvolume), extraction into chloroform and subsequent determination offluorescence on a silica gel thin layer chromatography.

The same procedures as described above were repeated except that,instead of liquid dimethyl ether, 450 g. of a mixture of liquid dimethylether with varied water content was employed as indicated in Table 1.The results are also shown in the same Table.

                  Table 1                                                         ______________________________________                                        Results of extraction of raw peanuts contaminated                             with 450 ppb of Aflatoxin with a solvent system of                            liquid dimethyl ether-water having varied water content                       Water content of                                                              the system, % (w/v)                                                                          0       1        3    6.1  30                                  Concentration of                                                              the remaining  400     350     10    9    95                                  Aflatoxin, ppb                                                                Amount of the residual                                                        defatted peanuts*, g                                                                         69.0    69.7    68.7  68.5 63.0                                ______________________________________                                         *calculated on the dry basis.                                            

EXAMPLE 1

Raw peanuts (water content 7.9%, crude fat 47.9% and crude protein28.2%) contaminated with 1,000 ppb of Aflatoxin were pulverized by meansof a silent cutter and passed through a 12 mesh sieve. Into a 2liters-volume continuous extraction tower was charged 400 g. of thepeanut powder thus obtained and subsequently continuous extraction waseffected with a flow rate of 0.1 liter/min. of liquid dimethyl ether atroom temperature for 60 hours. After completion of the extraction, theliquid dimethyl ether solution was filtered off to leave the peanutpowder (260 g.), analysis of which showed a total residual amount ofAflatoxin (B₁ and B₂) of 800 ppb (water content 4.2%, crude fat 0.9% andcrude protein 43.3%).

The defatted peanut (50 g., containing 800 ppb of Aflatoxin) of a lowprotein denaturation obtained as above was placed into a 1 liter-volumepressure resistant vessel equipped with a magnetic stirrer.

Subsequently, 25 ml. of water was added thereto and extraction waseffected with 70 g. of liquid dimethyl ether while stirring for 1 hour.The 6.1% water saturated liquid dimethyl ether solution containingAflatoxin was filtered off and the residue again extracted with 70 g. ofliquid dimethyl ether. Such extraction procedures were repeated sixtimes to yield 42.5 g. of the defatted peanut powder as an end product.The powder was treated in the same manner as mentioned above for thecomplete removal of the solvent and analyzed to show an Aflatoxinconcentration of 6 ppb, which means a substantially complete removal, aswell as water content 5.0%, crude fat 0.8% and crude protein 51.0%.

EXAMPLE 2

A peanut meal contaminated with 1.2 ppm Aflatoxin (prepared by pressingand extracting with n-hexane) was pulverized by means of a mixer andpassed through a 48 mesh sieve to gather 100 g. of the peanut meal(water content 2.5%, crude fat 3.0% and crude protein 48.0%). The mealwas well kneaded with 200 ml. of water and placed into the sameextraction vessel as in Experiment 1. Then, 450 g. of liquid dimethylether was added thereto and stirring was continued for 1 hour. Theliquid dimethyl ether solution containing Aflatoxin (saturated withabout 6% water) was transferred into a separate cooled pressureresistant vessel and the liquid dimethyl ether was recovered. The sorecovered liquid dimethyl ether (450 g.) was placed into a 1liter-volume pressure resistant vessel and reused for a subsequentextraction. Such extraction procedures were repeated nine times. Thetreated peanut powder thus obtained was subjected to the treatment forcomplete removal of the solvent to yield 98 g. of a peanut powdercontaining no substantial Aflatoxin, analysis of which showed Aflatoxincontent 4 ppb, water content 5.2%, crude fat 0.4% and crude protein49.0%.

EXAMPLE 3

Raw peanuts contaminated with 450 ppb of Aflatoxin were pulverized bymeans of a mixer and passed through a 20 mesh sieve to obtain 200 g. ofa peanut powder (water content 8.2%, crude fat 45.2% and crude protein26.7%). The peanut powder thus obtained was placed into a 1 liter-volumepressure resistant extraction vessel and extraction was effected with200 g. of water-saturated liquid dimethyl ether (containing 6.1% byweight of water) at room temperature while stirring for 40 minutes.After completion of the extraction, the liquid dimethyl ether solutionwas filtered off and the peanut powder thus separated was againextracted with a fresh 200 g. portion of water-saturated liquid dimethylether under the same conditions as mentioned above. Such extractionprocedures were repeated seven times. Subsequently, similar extractionprocedures were further effected by the use of 200 g. of liquid dimethylether free of water and once more repeated. Raw peanut powder wasseparated from the liquid dimethyl ether and the residual dimethyl etherwas completely removed therefrom at 40° C. under reduced pressure for 1hour. The peanut powder thus obtained (89 g.) was analyzed to show atotal Aflatoxin (B₁ and B₂) content 9 ppb, water content 2.7%, crude fat0.9% and crude protein 52.0%.

EXAMPLE 4

Raw peanuts contaminated with 1,000 ppb of Aflatoxin pulverized by meansof a meat chopper and passed through a 12 mesh sieve to yield 100 g. ofa peanut powder (water content 7.8%, crude fat 52.8% and crude protein26.5%). The powder thus obtained was placed into a 300 ml.-volumepressure resistant column with an inner diameter of 45 mm. Subsequently,water-saturated liquid dimethyl ether was slowly passed therethrough ata flow rate of about 6 ml./min. until a 2-liter volume thereof wasconsumed. The water-saturated liquid dimethyl ether remaining in thecolumn was completely recovered into a separate vessel with a differencein temperature. The peanut powder taken out of the column was thendehydrated with two 150 g. portions of liquid dimethyl ether free ofwater. The raw peanut powder thus obtained was separated from the liquiddimethyl ether and the residual dimethyl ether was completely removedtherefrom at 40° C. under reduced pressure for 1 hour. The raw peanutpowder (40 g.) was analyzed to show Aflatoxin content 4 ppb, watercontent 5.1%, crude fat 0.2% and crude protein 54.2%.

EXAMPLE 5

The peanut meal contaminated with 1,200 ppb of Aflatoxin (200 g.,employed in the Example 3 through a 48 mesh sieve) was extracted with400 g. of water-saturated liquid dimethyl ether while stirring at roomtemperature for 40 minutes. After completion of the extraction, theliquid dimethyl ether solution was separated by filtration from thepeanut meal powder, passed, as it was, through an 100 ml-volume pressureresistant column packed with 50 g. of granular activated carbon (soldunder tradename "Ajiencoal" and manufactured by Ajien K. K., Japan) toadsorb thereon the Aflatoxin in the solution. 400 g. of the liquiddimethyl ether recovered from the activated carbon column was againmixed with the peanut meal powder and extraction was effected at roomtemperature with stirring for 40 minutes. Such procedures were repeatedsix times. Then, twice extractions were effected with 200 g. of liquiddimethyl ether free of water followed by drying. The so obtained peanutmeal powder was treated in the same manner as mentioned above to removethe solvent therefrom completely. The peanut meal powder (102 g.) wasanalyzed to show Aflatoxin content 10ppb, water content 4.9%, crude fat0.3% and crude protein 49.7%.

EXAMPLE 6

Raw peanuts contaminated with 950 ppb of Aflatoxin were pulverized andsieved in the same manner as in Example 5 to yield 800 g. of the 20mesh-through meal (water content 8.2%, crude fat 49.7% and crude protein25.7%). The meal was charged into the same 2-liter volume extractiontower as in Example 1 and continuous extraction was effected with liquiddimethyl ether free of water at a flow rate of 0.2 liter/min. and roomtemperature for 1 hour. The tower was subsequently equipped with a 300ml-volume pressure resistant column containing 150 g. of granularactivated carbon and water-saturated liquid dimethyl ether was passedthrough the tower and column at a flow rate of 100 ml./min. for 2.5hours. After completion of the extraction, drying and solvent removingprocedures were conducted in the same manner as in Example 5 to yield382 g. of a peanut powder, analysis of which showed Aflatoxin content 12ppb, water content 6.2%, crude fat 0.4% and crude protein 50.2%.

EXAMPLE 7

Cotton seed cake contaminated with 200 ppb of Aflatoxin was pulverizedby means of a mixer and passed through a 20 mesh sieve. The resultingcotton seed cake powder (100 g.) was charged into the same 1liter-volume pressure resistant vessel as in Example 3 and 100 ml. ofwater was added thereto. Then, extraction was effected with 300 g. ofliquid dimethyl ether while stirring at room temperature for 30 minutes.Thereafter, a water saturated liquid dimethyl ether solution containingAflatoxin was filtered off and the residual cotton seed cake powder wasagain extracted with a fresh 300 g. portion of liquid dimethyl ether.Such procedures were repeated six times. The cotton weed cake powderthus obtained was treated under the same conditions as mentioned aboveto remove the residual liquid dimethyl ether. Yield 93 g.; Aflatoxincontent 3 ppb.

What is claimed is:
 1. A method for the removal of Aflatoxin fromcereals, oil seeds and feedstuffs contaminated therewith which comprisessubjecting said cereals, oil seeds and feedstuffs to at least oneextraction with liquid dimethyl ether and water at temperatures nothigher than those at which any proteins in said materials are thermallydenaturated, said water being employed in an amount of 2 to 8% by weightwith respect to the liquid dimethyl ether.
 2. A method according toclaim 1 wherein the water is employed in an amount of 3 to 7% by weightwith respect to the liquid dimethyl ether.
 3. A method according toclaim 1 wherein the water is employed in an amount of saturationsolubility to liquid dimethyl ether.
 4. A method according to claim 1wherein the liquid dimethyl ether is mixed with water and introducedinto the extraction system.
 5. A method according to claim 1 wherein thewhole amount of the water is once introduced into the extracting systemand the liquid dimethyl ether is stepwise added to the system in eachextraction step.
 6. A method according to claim 1 wherein said cereal,oil seed and feedstuff are raw or processed.
 7. A method according toclaim 1 wherein said oil seed is a raw peanut, a peanut meal or a cottonseed meal.
 8. A method according to claim 1 wherein said temperaturesare between 30° and -30° C.
 9. A method according to claim 1 whichfurther comprises contacting the liquid dimethyl ether -- water systemdischarged from the extraction system and containing Aflatoxin withactivated carbon to adsorb the Aflatoxin in said activated carbon, thusregenerating the liquid dimethyl ether -- water system.